Split circuit potash ore flotation concentration



May 27, 1958 W. A. SMITH ETAL Filed D60. 24, 1956 MINE RUN 0115' f CRUSHED TO =/e" BRINE .SCRUBBER +14 MESH UNDER-FLOW? CLASSIFIER ROD MILL -14 MESH ovERr-Low (-210 MESH) [To mums THICKENER HvoraosEPARA-roa UNDER-FLOW |4 MESH same OVERF'LOW MESH UNDERFLOW CLASSIFIER [+35 MEEH SLIME CONTROLLANT fififig; sum: CONTROLLANT 5.6. TERGITOL ADDED HERE B E. INE R| E F CONDITIONER CONDITIONER i TO SEPARATE FIN-E FRACTION F'LOTATLON CIRCUIT (ALTERNATIVE) FLOTATION o1= COMBINED FRACTIONS TO SEPARATE COARSE FRACTION FLOTATION CIRCUIT INVENTORS WILL/AM AUBREY SMITH VERNON L. MATTSON GENE MEYER ATTORNEY United States Patent SPLIT CIRCUET POTASH ORE FLQTATIQN CONCENTRATIGN William Aubrey Smith, Carlsbad, N. hiem, Vernon L.

Mattson, Wheat Ridge, Colo, and Gene Meyer, Shiprock, N. Mex assignors to T he American Metal Company, Limited, a corporation of New York Application December 24, 1956, Serial No. 633,253

3 Claims. (Cl. 209-166) The present invention relates to the froth flotation' of sylvite from potash ores. The invention will be described with particular reference to the treatment of sylvinite ores, such as, for example, those found in the Carlsbad district of New Mexico, but it is to be understood that it is applicable to the treatment of other potash ores wherein sylvite is associated with other minerals.

It has been known for some time that the sylvite Values of sylvinite ores may be concentrated by a froth flotation process in which chemical reagents of the cationic group are used as collectors for the sylvite values. The cationic group of collectors includes the high molecular weight aliphatic amines and their water-soluble amine salts, as well as quaternary ammonium salts. The following are typical examples of the cationic collectors that are commercially available: n-octylamine, n-decylamine, n-dodecylamine, n-tetradecylamine, n-hexadecylamine and n-octadecylamine, mixtures of the above mentioned amines in various proportions and the water-soluble acetate salts of such amines.

As borne out by statements found in various prior patents, it was considered necessary, until the recent investigations more particularly referred to hereinafter were made, to use a relatively high proportion of one of the cationic collectors in order to insure an acceptable concentration and recovery of the sylvite values of sylvinite and other sylvite-containing potash ores by a froth flotation process. When treating an ore feed prepared by crushing or grinding to the fineness normally considered necessary in bringing about a froth flotation concentration of the sylvite values, proportions of the amine collecting agent of the order of 0.8 to 1.0 lbs. per ton of ore were formerly generally specified. When it is borne in mind that sylvinite ores generally contain only from 30 to 40% of sylvite and that the recovery is not complete,

it will be understood that the reagent cost represents a substantial item of the overall cost of recovering sylvite from its ores and producing an acceptable commercial potash product.

A process whereby the requirement of collecting agent in the flotation concentration of the sylvite values of sylvinite ores may be very substantially reduced as compared with the prior practice in such a flotation operation is disclosed in U. S. Patent No. 2,724,499 which issued on November 22, 1955, from an application of the present inventors and Robert A. Baxter which was copending with application Serial No. 288,962 filed May 20, 1952, now abondoned, of which the present application is a continuation-in-part.

it is an object of the present invention further to reduce the reagent cost without impairing the flotation result;

It is a further object of the present invention to improve the recovery obtainable by the flotation treatment.

ice

It is a still further and important object of the present invention to improve the grade of the concentrate and more particularly to produce, directly as the result of the flotation treatment and without necessarily resorting to a subsequent sizing by screening, a plurality of concentrate fractions which are respectively more uniform as to the particle sizes and show less tendency to dusting than has been the case with the sylvite concentrates heretofore produced.

It is another important object of the invention to provide a split circuit flotation process wherein a relatively large proportion of the sylvite values of the flotation feed is recovered in the form of a more closely sized coarse fraction that is especially suited for use as a fertilizer.

Other objects and advantages of the invention will be come apparent from the detailed description.

We have observed that the tendency for sylvite-containing potash ores to consume an inordinate amount of a cationic collector is to a considerable extent due to the tendency of the finer particles of the ore as customarily prepared for the flotation treatment to consume a much larger proportion of the collector than is necessary for a satisfactory flotation result. Furthermore, the finer particles show this capacity for consumption of the collector equally as well when the collector is one of the higher molecular weight cationic collectors as is the case when lower molecular weight collectors are employed. At the same time it is observed that the lower molecular weight collectors, e. g., shorter chain amines, will by themselves sufficiently condition the finer particles for a flotation operation so that it is not necessary that such fine particles shall have attached to them any of the more expensive higher molecular weight collectors. On the other hand, the lower molecular weight collectors are generally not sufficiently effective to prepare the coarser particles of the ore feed for a flotation treatment.

We have further observed that if the ore for the flotation feed, after appropriate crushing or grinding, is screened or otherwise classified into fine and coarser fractions and these fractions are separately conditioned with appropriate collecting agents, it is possible to obtain a satisfactory flotation result with a much smaller overall quantity of the collecting agent or agents than has heretofore been considered necessary.

Besides the reagent economies that are made possible by separating the feed into a finer and a coarser fraction and separately conditioning the two fractions, we have found that further advantages are realized when the preparation of the ore feed for the flotation operation, i. e., the separation of the feed into a plurality of fractions according to particle size, usually two fractions, is so regulated as to produce a coarse fraction whereof the particles are of a size range that is so selected as to increase the separation of the sylvite particles from the halite or gangue particles of the ore according to their difierence in particle size during the preparation steps of the process. in this way the amount of processing of the coarser fraction in the flotation cells may be reduced and the scrubbing and mechanical desliming steps required to render the coarser fraction amenable to flotation may be materially reduced. A further practical advantage of this procedure resides in the fact that the upper limit on the size of the particles that can be floated in the coarse fraction can be increased, and the resulting concentrate is made a much more desirable commercial product from the standpoint of its granular character and flowability.

In determining the point of demarcation between the coarse and the finer ore fractions, advantage is taken of 3 v the observation that thehalite constituent of sylvinite and similar sylvite-containing ores 'is more friable than the sylvite constituent and consequently the halite particles tend to be reduced in the crushing and grinding steps to a considerably smaller average'particle size than the sylvite particles. For example, We have found that a substantially larger proportion of the halite particles, as compared to the sylvite particles, 'will have been reduced to 28 mesh when the crushing and grinding steps have been so conducted as to insure that the maximum size of the ore particles has been reduced to mesh As will be brought out further hereinafter, by carrying out the mechanical desliming and classifying steps so as to produce acoarse fraction of a particle size range between 10 mesh and 28.n1esh with the rest of the feed carried over into a finer fraction, it is not only possible to reduce the number of mechanical desliming steps applied to the coarser fraction but also to effect a very considerable saving in reagent costs both in respect of the amount and kind of collector used and also in respect of the amount of slime control reagent required to obtain a given grade of concentrate and a given recovery. This will be further explained in'the ensuing. description.

According to one embodiment of the invention-the ore is firstcrushed or groundto a" suitable degree either to bringall of the particles within the size range suitable for flotation or to a predetermined coarser size, and then is screened or classified to provide a plurality of fractions, one of which consists of particles of a predetermined size rangeincluding the finer particles that are to be floated and at least one coarser fraction. When the ore contains particles too coarse to be floated these coarser particles will be separated either in an initial screening or classify ing step or bylfurther classifying the coarser fraction remaining after the fine fraction has been obtained. 7

Usually. best results are obtained by excluding from the flotation feed all ore particles that will not pass a IO-mesh sieve. Preferably particles of finer than 270-mesh should also be excluded or will have been removed in the course a of. the preliminary desliming treatment that isusually applied in preparing the ore for the flotation operation. Witha flotation feed consisting of particles falling within the particle size range -l0 mesh plus 270 mesh, we have obtained very satisfactory results by separating the feed 7 into a fraction consistingprincipally of particles finer than ZS-mesh and a fraction that will pass a lO-mesh sieve but are coarser than 28-me sh." When the fractions of the feed are re-combined before the flotationstep, it

may be advisable to control the particle size of the feed so that it will all pass a l t-mesh sieve and in this case introducing into each fraction a suflicient quantity of colf lecting agent to prepare that fraction for the flotation treatment. For reasons of economy and to take advantage of the ability of the lower molecular weight cationic collecting agents, e. g., the shortercarbon chain aliphatic amines,

to reduce or eliminate the necessity for addition of a,

separate frothing agent, it is preferred to use, as the collecting agent for the finer fraction a lower molecular weight collecting agent or a. mixture, of lower molecular weight collectors. For the 'coarserfiaction, higher molecular' weight collectors will ordinarily be .required 1 and these will be-selected with regard to the size of the coarser particles. .Since the finer particles have a tendency'to absorb much more of a collecting agent than is necessary for their satisfactory flotation, care will be taken to determine in advance the proportion of collecting agent required to float the finer fraction,;and only that proportion need be added.

After the finer and coarser ore fractionshave been separately conditioned with appropriate amounts and kinds of collectors as above described, they are either floated separately or combined and then floated.

it will be understood that the ore will be pulped with brine, usually consisting of a saturated aqueous solution of the ore constituents, before it is separated into the appropriately sized fractions by a classifying procedure,

and that additional brine will beadded at appropriate stages between the classifying and mechanical desliming steps to maintain a suitable pulp density. Likewise, .suitable additions of brine will be added to the classified 'fractions before the collectors are added. It is usually ad eral class hereinbefore mentioned. I

pared with the priorjart practices by introducing an emulsifying agent either-along with the amine collector or at an earlier stage in the conditioning treatment. This improvement is particularly noticed in conditioning the coarser fraction, both from the standpoint of promoting the dispersion ofthe longer 'carbonchain amines and because there is a lessened tendency for large flocs to form.

Such agents'also actto stabilize the froth. When the coarser fraction is torbe floated separately it is also advisable to'add pine oil or another suitablefrothing agent, although the amount of such addition may be reduced or in some cases eliminated if an emulsifying agent is present.

ventional frother. When the two fractions are to be combined after conditioning and before floating, it :is usually best to add a small amount of a frother.

In addition to the savings in reagent costs that'are made possible by the separate conditioning of finer and coarser fractions of the flotation feed, We have observed that the higher molecular or longer chain amines are more effective 7 on coarser particle sizes. Accordingly, it is advantageous in conditioning a coarser fraction to exclude the fine particles from the coarser fraction and use a higher molec ular weight or longer chainamine as the collector, with or without widening of the particle size range to include particle'that are somewhat coarser than those heretofore considered suitable for a flotation feed.

It a will be understood that this opens up interesting possibilities because of the commercial demand for granular potash products that are coarser or have a coarser much in demand for .use in commercial fertilizers. .For

example, we have produced arelativ'ely uniform coarse product within the size range-10 mesh plus 28 mesh that finds ready acceptance as a. granular potash product and is remarkable for its freedom from tendency to dust-.

It will be understood, how- The flotation is'very substantially improved as com ing when undergoing packaging or other handling for shipping and when put to use for agricultural purposes. The concentrate recovered from the finer fraction also is a more desirable product because, being of more uniform particle size, it likewise shows a lessened tendency to dusting during handling.

For convenience there is set forth in the attached drawing a flow sheet illustrating in full lines one form of the process as it may be carried out in practice. Certain modifications of the procedure are indicated in dotted lines. It will be understood by those skilled in the art that variations in the procedure may be made without departing from the invention.

According to one procedure for carrying out the invention, run of mine ore is first subjected to dry crushing to /2". The ore is then pulped with a saturated brine composed of the sylvite and halite constituents of the ore. The pulp is then passed through a scrubber which may consist of a rotary drum carrying lifts for tumbling and mixing the ore and brine. Sufiicient brine is added at or immediately ahead of the scrubber to produce a pulp containing 60 to 70% solids. Unless it is contemplated that the ore will be subjected to an especially thorough mechanical desliming later in the process, it is desirable to add a ligno-sulfonate dispersing agent or an equivalent dispersing agent with the brine introduced in the initial pulping step sufiicient to insure the desired dispersing action on the slime. The pulp is passed from the scrubber to a classifier where additional brine is added. The operating condit ons at the classifier are advantageously so regulated as to insure that the overflow shall consist of a pulp containing ore particles of a suitable fineness for a flotation feed, for example, a fraction composed principally of particles passing through a ZO-mesh sieve. The underflow, consisting principally of the coarser particles in the form of a thick pulp, say 60% solids, is then diluted with additional brine to a suitable density for wet grinding, say to about solids, and then subjected to wet grinding to reduce such coarser ore particles to a suitable fineness for the flotation feed.

The pulp containing this ore fraction isthen combined with the -20 mesh fraction from the classifier overflow and the combined flow is subjected to a mechanical desliming treamient in a second classifier of a suitable type for slime removal, e. g. a hydroseparator. The rates of feed and agitation as well as other classifying conditions are so regulated during the deslirning step as to insure an overflow which contains largely -270 mesh particles of the ore and the insoluble slimes.

The underficw containing the rest of the ore is fed to a third classifier which may be of the conventional Dorr rake type or a cyclone separator. The operating conditions at this cia sifier are so regulated as to insure that the overflow shall consist of a pulp containing a predetermined finer fraction of the ore particles, for example, a fraction composed principaliy of particles passing through a 28-mesh or a 35-mesh sieve depending on the point at which the out between the coarser and the finer fractions is taken. This finer fraction and the underfiow from this classification step, which contains the coarser fraction of the feed, are then separately conditioned with.

suitable proportions and kinds of amine collectors. Usually it will be found desirable to regulate the amounts of the amines added to the separate fractions of the feed so as to insure that a higher proportion of the amines, based on the weight of the ore, is added to the finer ore fraction than is added to the coarse: fraction. As pre viously pointed out, further economy in the amine requirement will be realized when the finer fraction is conditioned With lower molecular weight or shorter carbon chain amines. It will usually be necessary or at least desirable to use an amine collector consisting of or con taining principally higher molecular weight amines for conditioning the coarser fraction.

As indicated in dotted lines on the flow 5 heat. it will usually be desirable to provide a small addition of a slime control agent to the respective finer and coarser fractions of the ore pulp at points in the divided circuit between the third classifier, or mechanical desh'ming stage, and the respective amine conditioning stages of the process. As shown, it is preferable to add a larger proportion of the total amount of the slime control agent to the finer fraction of the ore since the surface areas of the ore particles will in the aggregate be greater than those of the coarser fraction and the proportion of adhering slime will tend to be correspondingly greater. Various known slime control agents may be used, e. g., starch. We prefer, however, to use as the slime control agent a polyglycol or a polyglycol ether of the class disclosed in U. S. Patent No. 2,724,499 or a mixture of slime control agents including a polyglycol or polyglycol ether and a water-solubie acrylonitrile polymer (6. g. X-26l0 sold by Dow Chemical Co), Guartec, a mannose polymer sold by General Mills, inc, or Lytron 886, a vinyl acetate-maleic anhydride copolymer sold by Monsanto Chemical Co. It is generally more economical to provide a controlled small addition of a slime control agent in advance of the amine conditioning step than to repeat the mechanical deslirning treatment to the point where a substantially complete removal of insoluble slime is insured.

The advantages of the invention will be made further apparent from the following examples:

Example 1.A 1,000 mg. sample of -14 mesh sylvinite ore from the Carlsbad district prepared by grinding to 14 mesh a sample of /2 plus 14 mesh ore was made into a pulp with a saturated brine of the ore constituents, then introduced into a Fagergren three liter laboratory flotation celi, agitated for five minutes and then deslimed by settling one minute, siphoning to a depth of 4 /2" from the top of the bowl, then refilling the bowl with saturated brine to the overflow and agitating for one minute. These operations of settling, siphoning, refilling and agitating were repeated four times.

The deslimed ore sample was then screened over a 35 mesh sieve. The +35 mesh fraction was then placed in a 6 I. D. glass bottle with suflicient brine to bring the pulp density to solids. One cc. of a solution of Tergitol TMN 650 was added followed by agitation by rolling the bottle at 97 R. P. M. for two minutes. Three cc. of a 2% solution of Arma-c TD were then added followed by agitation for 30 seconds. The 35 mesh fraction was conditioned in a similar manner with the same reagents and agitation conducted in the same way first for two minutes following addition of the Tergitol and later for 30 seconds following the amine addition. In this case 1 cc. of Tergitol TMN 650 were added in the first stage and, after agitation as before for two minutes, one cc. of a 2% solution of Armac TD was added followed by further agitation for 30 seconds. The Tergitol compound acts as a slime control agent thereby reducing the amine requirements. In addition it acts to stabilize the froth and render it more persistent. Tergitol TMN 650 is the trade name of a polyglycol compound manufactured by Carbide & Carbon Chemicals Co. The numerical designation refers to the approximate molecular Weight of the compound.

The total amounts of the two reagents corresponded to a proportion of 0.10 lb. of Tergitol TMN 650 and a proportion of 0.16 lb. of Armac TD per ton of ore. Because the slime content of the finer fraction was relatively greater than the slime content of the coarser fraction, a relatively large proportion of the total amount of the TMN 650 was added to the finer fraction and a corresponding relatively small proportion of the TMN 650 was added to the coarser fraction. On the other hand, because the require ment of amine for flotation of the finer particles is less than for the coarser particles, relatively small proportion of the total amount of Armac TD was added to the er fraction, and the proportion added to the coarser fraction was increased accordingly. The two separately conditioned products were thereafter combined, transferred to the Fagergren cell and floated for threejminutes. The results were as follows:

' KOl' Percent Percent Percent Percent K01 Product Weight \Veight a Weight Distri- 7 Original bution Ore Cones. 335.1 37. 3 97. 2 3e. 3 97. 1 .Taillng 564.4 62.7 1.8 1. 1 2. 9

Example 2.--For comparison purposes an identical sample of sylvinite ore was deslimed and conditioned for flotation in the same manner as described above except that the deslimed ore sample was not screened and separated into a +35 mesh' and'a 35 mesh fraction. The same total amount of reagents in proportion .to the total amount of the ore were used. The conditioned ore was floated for 3 minutes with the following results:

. a K01 Percent Percent Percent Percent K01 Product Weight Weight K01 Weight Distri- Original bution Ore Cone 308.1 33.9 96.2 32.6 84.9 Tailing 600. 4 66. l 8. 7 5. 8 l5. 1

brine to a density of approximately 60% solids. Five'cc.

of a'2% starch solution was'then added and the mixture was then agitated for 2 minutes. Three cc. of a 2% solution of Armac TD were then added followed byfurther' The 35 mesh fraction was agitation for 30 seconds. conditioned by adding 7 /2 cc. of 2% starch solution and then agitating for 2 minutes. One cc. of a 2% solution of Armac TD was then added followed by further agitation for 30'seconds. Because the finer fraction carried a 7 higher proportion of slimes than the coarser fraction, a

relatively largeproportion of the total amount of starch was added to the'finer fraction. On the other hand, a relatively small proportion of the total amount of Armac TD was added to the finer fraction. The two separately a conditioned products were'th'en combined and transferred to the Fagergren cell. Methyl isob'utyl carbinol in the proportion of 0.05 lb. per ton of ore was added at this point. .The conditioned pulp wasthen floated for 3 minutes with the following results:

' KCl Percent Percent Percent Percent KC] Product Weight Weight K01 Weight Distrip a V Original bution V Ore 'Conc'. 7 379.2 40.9 93.6 38.3 98.0 Telling 547. 2 59. 1 l. 3 0. 8 2. 0

Example 4.- A. 1,000 gm. sample of the same ore prepared as described in Example 1 was pulped and 'deslirned four times as described in Example 1. After fur-. ther classification to form a 35 mesh fraction and a +35 mesh fraction, these fractions were separately con;

ditioned'for flotation inthe samemanner and with the same relative proportioning of the slime control and amine collecting agents as described in Example 3 except that Tergitol TMN 650 in the total. proportion of. 0.10 leper ton of ore was added in place of starch. The results of the flotation treatmentwere as follows:

Percent K01 Distributton 1101 Percent Weight Original Ore ' Percent Percent Product Weight Weight K01 Cone Telling Example 5 .A 1,000 gm. sample of Carlsbad sylvinite ore crushed to l4 meshin a coffee mill and rolls was made into a pulp and deslirned four times in the same manner .as described in the preceding example s. The

deslimed ore sample was then screened over a 35 mesh sieve. The 35 mesh fraction was then again pulped with brine to a densityof about 60% solids. One cc. of a2% solution oi Tergitol TMN 650 was then added and the mixture was'agitated by stirring for 2 minutes. Thereupon 3 cc. of Armac TD was added and'themixture was then further agitated for 30 seconds.- The -35 mesh fraction was similarly pulped and 1 /2 cc. of 2% Tergitol TMN 650 was then added followed by agitationfor 2 minutes. One cc. of Armac 8-D was then added followed by agitation for 30 seconds. Armac 8-D consists chiefly of the acetate of normal octylamine. The total amounts of the respective reagents corresponded to the following proportions per ton of ore: f 0

0.10 lbs. Tergitol TMN 650 0.12 lbs. ArmacTD 0.04 lbs. Armac 8-D The two products were thereafter combined in the Pager gren cell and floated for 3 minutes. The results were as follows:

Percent Distribution K01 Percent Weight Original 7 Ore Percent Percent .Product Weight Weight K01 Cone 'lailing Mon POI

Example 6.A 1,000 gm. sample of Carlsbad sylvinite ore previously crushed to /4" was screened over af20 mesh sieve. Brine was added to the +20 mesh fraction to form a pulp containing 25% solids. The ore pulp was then introduced into a laboratory ball milland ground for 2 minutes and 45 seconds. The product was then combined with the 20. mesh fraction and introduced into a Fagergren laboratory flotation cell along with Marasperse CB in the proportionof 0.50 lb. of Mara sperse per ton of ore. The mixture was then conditioned] by operating the cell at 1.070 R. P; M. for 5 minutes, whereupon the pulp was allowed to settle 2 minutes and then siphonedto a'depth of 4 /2 from the top of the bowl. 'Fresh' brine was then added to the product remaining in the cell and it was then again rotatedfor 1 minute followed by settling for 2 minutes and siphoning as before. This operation was again repeated, making a total of three desliming treatments. The deslimed product was then screened over a 35 mesh sieve.

The +35 mesh fraction was then returned to the cell and pulped with a brine to a density of about 20% solids' Three cc. of a 2%.. Armac TD solution was added and the whole was conditioned by agitation for 30 seconds.

The 35 mesh fraction was similarly conditioned by, adding '1 cc. of the 2% Armac TD solution followed by agitation for 30 seconds.

K01 Percent Percent Percent Percent K01 Product Weight Weight K01 Weight Distri- Original bution Ore Cone 369.3 39.8 96.9 38.6 99.0 Talling 559. 6 60. 2 0.6 0. 4 1.0

The Marasperse CB addition was added to promote the dispersion of the insoluble slimes present in the ore and thus facilitate their removal in the mechanical desliming steps. This compound is a ligno-sulfonate manufactured by The Marathon Chemical C0., Rothschild, Wisconsin.

Example 7.A 1,000 gm. sample of Carlsbad sylvinite ore prepared as described in Example 1 was pulped and deslimed 8 times as described in Example 1. After further classification to form a 35 mesh fraction and a +35 mesh fraction these fractions were separately conditioned for flotation in the same manner as described in the next preceding example, except that in this case the total proportion of Armac TD was reduced to 0.10 lb. per ton of ore, no Marasperse CB was added to aid in the desliming of the ore and no addition of B-23 was added to the combined products of the separate amine conditioning steps. As in all of the preceding examples Where finer and coarser fractions were separately conditioned, a relatively small proportion of the total amount of the amine was added to the finer fraction with a corresponding increase in the proportion added to the coarser fraction. To be more specific, 2 cc. of a 2% solution of Armac TD were added to the +35 mesh fraction and /2 cc. of the solution was added to the -35 mesh fraction. The following results were obtained:

obtained without the use of slime control agents or emulsifying agents when the ore has been very thoroughly deslimed and the collecting agent is added in suitable proportions separately to finer and coarser fractions of a flotation feed.

The collectors designated as Armac 8D and Armac TD are manufactured and sold by Armour & Company. Armac 8D has been previously identified as to composition. Armac TD is understood to consist of a mixture of the water-soluble acetate salts of normal hexadecyl-, octadecyl-, and octadecenylamines.

Due to the relative insolubility of the higher molecular weight amines such as those contained in Armac TD and the difficulty of obtaining satisfactory dispersion of such amines in brine without violent mechanical agitation, it is usually preferable to take special steps to bring about their dispersion in the pulp. Such dispersion may be facilitated by introducing the amines in the form of a finely divided spray or through the use of an emulsifying or wetting agent.

We claim:

1. The improvement in the recovery of sylvite from potash ores which comprises subjecting a potash ore containing sylvite, and previously reduced to a degree of sub-division within the particle size limits for a froth flotation concentration, to a sizing treatment to provide at least two fractions, one composed principally of finer particles of said ore and the other composed of coarser particles of said ore, pulping said fractions with a saturated aqueous solution of the soluble ore constituents, separately conditioning said fractions for froth flotation concentration by adding to the finer fraction a cationic collecting agent of relatively low molecular weight and adding to the coarser fraction a cationic collecting agent of relatively high molecular weight, agitating the pulp to efiect thorough distribution of the collecting agent added to each fraction, and thereafter subjecting the conditioned pulp to froth flotation concentration.

2. The improvement in the recovery of sylvite from sylvite-containing potash ores which comprises subjecting sylvite-containing potash ore of a degree of sub division within the particle size limits for a froth flotation concentration, to a sizing treatment to provide at least two fractions, one composed principally of finer particles of said ore and the other composed of coarser particles of said ore, pulping said fractions with a saturated aqueous solution of the soluble ore constituents, separately conditioning said fractions for a froth flotation concentration by adding to the finer fraction a cationic collecting agent of relatively low molecular weight and adding to the coarser fraction a cationic collecting agent of relatively high molecular weight, agitating the pulp to effect thorough distribution of the collecting agent added to each fraction, thereafter ccm bining said conditioned pulp fractions and then subjecting the combined pulp to a froth flotation treatment.

3. The improvement in the recovery of sylvite from potash ores which comprises subjecting a potash ore containing sylvite, and previously reduced to a degree of sub-division within the particle size limits for a froth flotation concentration, to a sizing treatment to provide at least two fractions, one composed principally of finer particles of said ore and the other composed of coarser particles of said ore, pulping said fractions with a saturated aqueous solution of the soluble ore constituents, separately conditioning said fractions for froth flotation concentration by adding to the finer fraction a cationic collecting agent of relatively low molecular weight and adding to the coarser fraction a cationic collecting agent of relatively high molecular weight, agitating the pulp to effect thorough distribution of the collecting agent added to each fraction, and thereafter separately s 1- jecting the conditioned pulp fractions to froth flotation concentration.

4. The process according to claim 3 wherein the sizing treatment is regulated to provide a finer fraction consisting substantially all of particles -28 mesh in size and the coarser fraction consists substantially all of particles within the particle size range between 10 mesh and 28 mesh.

5. The improvement in the recovery of sylvite from potash ores which comprises subjecting a potash ore containing sylvite, and previously reduced to a degree of sub-division within the particle size limits for a from flotation concentration, to a sizing treatment to provide at least two fractions, one composed principally of finer particles of said ore and the other composed of coarser particles of said ore, pulping said fractions with a saturated aqueous solution of the soluble ore constituents, separately conditioning said fractions for froth flotation concentration by adding thereto a cationic collecting agent in a proportion for each fraction regulated to sub stantially satisfy the requirement for the collection and flotation of such fraction, agitating the pulp to effect thorough distribution of the collecting agent added to vpulp to froth flotation concentration 6. The process according to claim 5 wherein the sizing treatment is regulated to provide a finer fraction consisting substantially all of particles 28 mesh in size and the coarser fraction consists substantially all of particles within the particle size range between 10 mesh and 28 mesh and the conditioned pulp fractions are separately subjectedto froth flotation concentration to produce a relatively uniform coarse granular product from the coarse fraction and a relatively non-dusting finer product from the finer fraction. a r a 7. The process according to claim 5 wherein the sizing treatment is regulated to provide a finer fraction COD: sisting substantially all of particles -35 mesh'in size and the coarser fraction consists substantially all of particles within the particle size range between 14 mesh and 35 mesh' and the conditioned pulp fractions are separately subjected to froth flotation concentration to produce a relatively uniform coarse granular product from the coarse fraction jand a relatively non-dusting.

finer product from the finer fraction.

8. The process according to claim 5 wherein a slime i control agent is added to the separately pulped fractions at a stage in the conditioning thereof prior to the addition of the cationic collecting agent, the proportion of said slime controls agent added to the finer fraction being greater with respect to the amount of ore particles present therein than the proportion of slime control 'agent' added to the coarserrfraction bears to the amount of ore particles present in said coarser fraction. 7

References Cited in the file of this patent V UNITED STATES PATENTS i s 

1. THE IMPROVBEMENT IN THE RECOVERY OF SYLVITE FROM POTASH ORES WHICH COMPISES SUBJECTING A POTASH ORE CONTAINING SYLVITE, AND PREVIOUSLY REDUCED TO A DEGREE OF SUB-DIVISION WITHIN THE PARTICLE SIZE LIMITS FOR A FROTH FLOTATION CONCENTRATION, TO A SIZING TREATMENT TO PROVIDE AT LEAST TWO FRACTIONS, ON COMPOSED PRINCIPALLY OF FINER PARTICLES OF SAID ORE AND THE OTHER COMPOSED OF COARSER PARTICLES OF SAID ORE, PULPING SAID FRACTIONS WITH A SATURATED AQUEOUS SOLUTION OF THE SOLUBLE ORE CONSTITUENTS, SEPARATELY CONDITIONING SAID FRACTIONS FOR FROTH FLOTATION CONCENTRATION BY ADDING TO THE FINER FRACTION A CATIONIC COLLECTING AGENT OF RELATIVELY LOW MOLECULAR WEIGHT AND ADDING TO THE COARSER FRACTION A CATIONIC COLLECTING AGENT OF RELATIVELY HIGH MOLECULAR WEIGHT, AGITATING THE PULP TO EFFECT THOROUGH DISTRIBUTION OF THE COLLECTING AGENT ADDED TO EACH FRACTION, AND THEREAFTER SUBJECTING THE CONDITIONED PULP TO FROTH FLOTATION CONCENTRATION. 